1. Field of the Invention
This invention relates generally to an improved arrow and, more particularly, to an improved arrow system including an adjustable weight point, a nock with an integral and adjustable weight insert, an improved shaft, and integral means for broadhead point alignment.
2. Prior Art
Primitive arrows generally consisted of reeds or branches and the points thereof generally comprised chipped stone.
Modern arrows, on the other hand, include shafts which may be solid wood, metal tubes, woven fiber shafts, or composites thereof.
Solid wood shafts may be manufactured from standard port orford cedar, compressed cedar doweling, compressed cedar with an attached hardwood foot, or a tapered outer diameter (barreled) solid wood shaft; i.e. having an outer diameter which is larger in the center section than it is at either end. These solid wood arrows generally include points which were formed of metal and glued on to the wood shaft.
The woven fiber shafts include fiberglass, graphite boron, or combinations thereof. These shafts exhibited an improved durability and consistency; however, in their less expensive forms (i.e. fiberglass) these arrows are relatively heavy and not uniformly straight. Some arrows of various materials are characterized by solid shafts (used mostly as "fishing" arrows). Also the shafts may comprise tubes having parallel and constant outer and inner diameters or may be tapered smaller towards the rear end of the arrow with uniform wall thickness. This results in an arrow which is fragile at the rear of the tube, very strong at the front end of the tube but too weak in the middle section of the tube. These arrows were made this way to simplify dismounting from a mandrel over which the fibers are wrapped during manufacture of the tube.
Metal tube shafts are durable, consistent, and are generally lighter and faster flying than arrows made of either solid wood or tubular fiberglass tubes. Metal arrows are generally manufactured of stainless steel or aluminum. Unfortunately, making metal shafts which exhibit a required stiffness generally meant making them heavier than desirable.
Metal tube shafts are generally characterized by uniform wall thickness having parallel and constant outer and inner diameters. Aluminum arrow shafts were used wih increasing frequency when compound bows become popular around 1970. Compound bows made it possible for the average archer to draw and hold much heavier peak weights in drawing the bow, imparting greater thrust to the arrow shaft. This created a market for stiffer, lighter shafts than were possible when using either solid wood or fiberglass materials.
The metal shafts may be solid, or, as stated above, may comprise tubes having a uniform outer diameter and inner diameter. On the other hand, the tubes may be tapered toward each end (similar to the barreled shafts discussed earlier). These barreled shafts begin as shafts having a uniform wall thickness, however, a swedging process was employed that reduced the outside diameter at each end of the shaft and also thickened the wall of the tubes at the end of the shaft. Unfortunately, reinforcing is needed at the center of the shaft so as to stiffen the shaft against bending as it is being propelled from the bow.
Other metal and fiber shaft tubes have a uniform wall thickness but are tapered towards the rear of the shaft. These are typically swedged over a mandrel along its full length. The mandrel is then removed.
Finally, composite arrow shafts may include any of the already mentioned formations of solid or tubular structures and are made of combinations of various materials. For example, fiberglass and graphite, graphite and aluminum tubing, and aluminum tubing filled with styrofoam.
Throughout history, changes in arrow design have followed major changes in the design of bows used to propel the arrows. In some cases, major changes in arrow design have been delayed for long periods of time awaiting advances in material technology.
Initially, arrows were made from reeds or branches and served very well at that point in time since bows in those early days were very inefficient and incapable of providing uniform performance. Accuracy was not that important since arrows were generally lofted into the air by the thousands to fall upon the enemy from above. Individual targets were the exception rather than the norm.
During the period from about 1916 to 1935, bows of the "long bow" type were becoming more consistent in performance due to the use of better wood shaping tools. Thus, more uniform arrows were required. Since archery, at this time, was recreational in nature, individual accuracy had become of paramount importance. Arrows were shot "off the shelf" or sometimes using the top nuckle of the archer's bow hand as an arrow rest while the arrow was being drawn in aim. Bows were thickest at the point where the archer held them while shooting since this was the area under greatest stress and reinforcement was needed to reduce possibility of breakage. As a result, the arrow pointed off to the right or left of the target (depending on whether the archer was right or left handed). This led to what is commonly referred to as the "archer's paradox".
The "archer's paradox" relates to an arrow's attempt to have the point of the arrow and the rear tip of the arrow travel in the same straight line to the target even though the point started off to the right or left of the line between the archer and the target. The rear of the shaft, on the other hand, travels in a straight line down the center of the bow limbs and straight toward the intended target. As the back of the arrow travels straight toward the target with the bow string guiding it, the front of the arrow (the point) tries to bend around the bow and follow the same path toward the target that the rear end of the shaft is taking. This causes the arrow to bend in the center, usually too much so, so that by the time the string has completed its travel, the arrow is actually pointing to the opposite side of the target than it did when it started out. To offset this oscillation, feathers were added to the rear of the shaft to create a parachute effect; i.e. dragging the rear of the shaft in a straight line toward the center of the target. This, in effect, amounted to "steering" the arrow from the rear until the shaft column itself was free of oscillation and traveling in a straight line to the target.
With respect to the shaft column itself, care had to be taken to assure that the exact amount of stiffness be built into the shaft column itself. If the shafts were too stiff, the column would not bend enough around the bow to travel straight to the target, and if the shaft were not stiff enough, the feathers would not be able to pull the arrow back in line for the target. This posed some involved problems for arrow makers due to the fact that a great number of variables are involved. Each bow imparts a different amount of thrust to the arrow, and small changes in bow thrust could render an arrow that shot perfectly from one bow useless when shot from a bow with a different thrust.
From about 1935 to 1945, changes in bow designs again dictated improvements in arrow design. Bows of this period comprised laminations of two materials to create bows capable of imparting both greater amounts of thrust to the arrows in a more uniform manner. Laminations in and of themselves were not a new idea but were resurrected to be used in conjunction with new materials. For example, bows now become primarily laminations of hard rock maple sandwiched between sheets of fiberglass. The fiberglass added consistency and strength, prevented warpage, and resisted the bow's tendency to "take a set" when strung for extended periods of time.
As bows become more efficient, similar demands were placed on arrows. A popular shaft during this period was one of compressed cedar (although other shaft types were also available). The compressed shaft was straighter, less subject to warpage, and could accept greater amounts of stored energy from the bow while, at the same time, rendering more consistent results.
Bows of this period also began to use a "shelf" for resting the arrow on while drawing and shooting. Bows also began utilizing a "grip" section for the first time which was cut into the wood handle. This was now possible since the fiberglass laminates added enough extra strength to the bow handle so that removal of some material in this area did not unreasonably weaken the bow or render it prone to breakage. This "shelf" was, in reality, hardly more than a notch, and therefore arrow design and manufacture still had to take the archer's paradox into account.
Between 1945 and 1969, the "recurved" style of bows was resurrected to take advantage of the new materials and laminating technologies then available. The combination of recurve action and more modern materials and laminating technology increased the amount of stored energy in bows being transmitted to the arrows significantly so as to cause archers to seriously consider alternatives to wooden arrow material.
Bows of this period also extended the arrow "shelf" area into a somewhat larger area that became known as the "sighting window". Notwithstanding, bows continued to be made primarily of wood laminated between fiberglass covers. As a result, the "window" was generally still fairly shallow and the archer's paradox continued to be a factor in all arrow design.
During this period, some experimentation was under way dealing with bow handle sections made of metal. During this evolutionary period, two materials were considered to be serious contenders for arrows. These were (1) tubular aluminum and (2) tubular fiberglass. Both were more durable than wood and able to absorb energy from the bow more efficiently. However, both types of arrows were significantly higher priced since glass and aluminum technologies were at that time less sophisticated. Notwithstanding, it was still necessary to engineer into the shaft column the exact degree of stiffness necessary to accommodate the old archer's paradox.
The first "compound" bows made their first commercial ppearance circa 1969. Compound bows consist of a center "handle" section to which two extremely stout bow limbs are bolted. The limbs each have mounted on their tips an eccentric pulley system. Such arrangements permitted the average archer to use bows which were roughly twice as powerful as they had been able to use previously.
This served to rush the conversion from wood to fiber or metal arrows since inconsistencies in wood arrows appeared greatly magnified in degree when shot from bows providing twice the effective push on the arrow. Even at this stage, however, bows continued to be made primarily of wood and glass laminates in both the limb section and the handle or grip section. The wood cut-out "sight window" remained fairly shallow and arrow design continued to utilize the old archer's paradox formula. On the other hand, arrows increased in size so as to be compatible with and able to accept the increased thrust of compound bows.
In or about 1975, a simplified version of a compound bow was introduced. It had a similar pulley system and utilized cast aluminum for the handle section onto which the limbs and pulleys were bolted. This bow included a metal hand "riser" (grip section) to accommodate the compound bows need for greater strength handle material, and stouter limbs attached/bolted to the handle section. Through the use of new casting or forging technologies in manufacturing the "handle riser" section of the bow, the sight windows could be cut farther into the line of the bow handle center. In fact, some were cut past the center line of the bow handle. Thus, finally, it was no longer necessary to consider the archer's paradox in arrow design; however, the existing arrow manufacturers continued to do so. This may be due to the fact that they did not realize that the archer's paradox no longer represented a problem or it may be that manufacturer's chose to use their existing tooling to manufacture arrows. It may be speculated however that old technologies continued to be used to enable the manufacturer to sell more arrows since each size of arrows had a very limited range of bow draw weights over which it could be expected to perform well. Thus, very small changes in bow thrust made it necessary to buy all new arrows.
To impart a complete understanding, a few points should be made regarding arrow points, feathers (fletching), and nocks.
From primitive times to present, feathers have been used to stabilize arrow oscillation in flight. These oscillations were introduced as a result of the archer's paradox accommodation in arrow shaft engineering. In recent times (since the 1960s), plastic replicas have found prominence as a substitute for turkey or other features as fletching materials.
Arrow points have evolved from chipped flint tied onto the shaft with raw hide to formed metal parts which are glued to the arrow and, most recently, to male screw-in tips which are seated in a female insert which is glued inside the tube forming the arrow shaft.
That portion of the arrow which accommodates the bow string is referred to as the nock and has evolved from hand carved notches in wooden shafts to plastic parts glued onto a wood taper or glued onto an insert in the arrow tube provided for the purpose of gluing a nock thereon.
Manufacturers of individual parts or components of the shooting system have, in the past, generally produced individually improved components without regard to their effect on other components in the system and the system in its entirety. In most cases, the effects on the overall shooting system performance were unknown or misunderstood.
Nevertheless, there are certain basic requirements for optimum performance which remain unchanged. First, the arrow must have adequate stiffness so as to absorb energy from the bow and not buckle in the center so severely as to become unstable in flight due to harmonic vibrations and oscillation. Second, they must be durable so as to be used and reused. Third, the arrow must be light enough to attain high speeds and heavy enough to prevent the bow limbs from retaining so much energy when the arrow is cast that the limbs are damaged when they slam to a stop at the end of the string's forward travel. This is tantamount to "dry firing" the bow and may cause severe damage to the bow. Fourth, and overlooked until relatively recently, it is extremely important that the arrow be properly balanced to attain good arrow flight. An arrow with too little weight at its front (point weight) will tend to tumble. Arrows must have extra weight at the front end to provide a guidance system for the remainder of the shaft in flight. Fifth, all other things being equal, if two arrows are shot from the same bow with the same initial thrust, the one lighter in mass weight will attain the higher velocity. However, as noted earlier, the arrow should not be so light as to allow the bow limbs to slam hard against the string at the end of its forward travel possibly damaging the bow itself.